부산대학교 도서관

In this article, the impact of gamma ( $\gamma $ ) irradiation on passivated and unpassivated AlGaN/GaN HEMT is presented in detail. Passivated and unpassivated GaN-HEMT devices have been exposed to $\gamma $ -radiations to a total dose of 10 kGy. Post- $\gamma $ -irradiation, a refinement in ohmic contact, which makes device source/drain, is recorded. Alteration in Schottky gate electrical characteristics ( ${C} - {V}$ and ${I}\!\!-\!\!{V}$ ) along with advances in device drain current and transconductance has been observed in unpassivated HEMT, while it remained almost unaltered in passivated GaN-HEMT after $\gamma $ -irradiation. The OFF-state gate leakage has deterioration in both types of HEMTs, suggesting a modification in trap concentration beneath the gate and near gate region during $\gamma $ -exposure. This is confirmed via pulsed ${I}\!-\!{V}$ measurements. A strong upswing in drain current recovery after stress bias is recorded post- $\gamma $ -irradiation in both types of HEMTs. This confirms that the trapping sites have been altered during $\gamma $ -exposure. Possible reasons causing this modification are improvement in gate metal barrier inhomogeneities and reduction/rearrangement of crystal defects during $\gamma $ -exposure . The effect of $\gamma $ -radiation on intrinsic/extrinsic device parameters has also been determined using S-parameters measurements. Intrinsic/extrinsic device parameters of passivated HEMT are observed to be less affected by $\gamma $ -irradiation in comparison to unpassivated GaN-HEMT devices, and post-radiation, both the devices have similar device parameters values as it was prior radiation making it suitable for harsh environment applications.